Composite coupling

ABSTRACT

Described herein are composite devices comprising two members. The first member is a heat recoverable driving member and the second is a metallic member associated with the first in such a way that upon heat recovery of the driver, the second member is dimensionally altered to engage a substrate. In one embodiment, useful for example as a composite coupling for joining cylindrical substrates, the driver comprises a tubular heat recoverable compression sleeve having a generally uniform interior surface. In this embodiment, the second member comprises a tubular insert snugly, and concentrically disposed within the sleeve. Although both its interior and exterior surfaces may be uniform, preferably one or both surfaces has a weakened portion to facilitate its deformation or bears integral radial teeth or a combination thereof. Upon heat recovery of the compression sleeve, the insert is compressed about the substrate. 
     In another embodiment, the driver is positioned internally of the second member. Expansive heat recovery of the driver expands the second member to engage the substrate. 
     In other embodiments, one or more members of the device can be made from a gall-prone metal to facilitate engagement of the device to a substrate or to facilitate engagement between members of the device.

RELATED APPLICATIONS

This application is continuation of application Ser. No. 572,838, filedJan. 23, 1984 which is a continuation of application Ser. No. 118,867filed Feb. 6, 1980, now U.S. Pat. No. 4,469,357, which is a continuationof application Ser. No. 608,209, filed Aug. 27, 1975, which is acontinuation-in-part of my copending application Ser. No. 404,723 filedOct. 9, 1973 entitled "Composite Coupling" and a continuation-in-part ofmy copending application Ser. No. 404,724 filed Oct. 9, 1973, both nowabandoned the disclosures of which are incorporated by reference.

FIELD OF THE INVENTION

This invention relates to heat recoverable devices. More specifically,it relates to a heat recoverable composite device for joining tubularsubstrates.

BACKGROUND OF THE INVENTION

Heat recoverable articles, i.e. those which have been deformed from afirst heat-stable configuration to a second heat-unstable configurationand which are capable of returning, or recovering, towards said firstconfiguration upon the application of heat alone, have found manyapplications in diverse fields. Such articles have typically been madefrom polymeric materials, especially cross-linked polymers, and havebeen described, for example, in U.S. Pat. Nos. 2,027,962 (Currie) and3,086,242 (Cook et al).

Quite recently, it has been discovered that such articles can be madefrom certain metals, sometimes called "memory metals" or "memoryalloys". These metal exhibit changes in strength and configurationalcharacteristics on passing through a transistion temperature, in mostcases the transition temperature between the martensitic and austeniticstates, and can be used to make heat recoverable articles by deformingan article made from them whilst the metal is in its martensitic, lowtemperature, state. The article will retain its deformed configurationuntil it is warmed above the transition temperature to the austeniticstate when it will recover towards its original confiuration. Thedeformation used to place the material in the heat-unstableconfiguration is commonly referred to as thermally recoverable plasticdeformation and can also, in certain cases, be imparted by introducingstrains into the article above the transition temperature, whereupon thearticle assumes the deformed configuration on cooling through thetransition temperature. It should be understood that the transitiontemperature may be a temperature range and that, as hysteresis usuallyoccurs, the precise temperature at which transition occurs may depend onwhether the temperature is rising or falling. Furthermore, thetransition temperature is a function of other parameters, including thestress applied to the material, the temperature rising with increasingstress.

Amongst such memory metals there may especially be mentioned variousalloys of titanium and nickel which are described, for example, in U.S.Pat. Nos. 3,174,851, 3,351,463, 3,753,700, 3,759,552, British Pat. Nos.1,327,441 and 1,327,442 and NASA Publication SP 5110, "55-Nitinol-TheAlloy with a Memory, etc." (U.S. Government Printing Office, Washington,D.C. 1972), the disclosures of which are incorporated herein byreference. The property of heat recoverability has not, however, beensolely confined to such titanium-nickel alloys. Thus, for example,various beta-brass alloys have been demonstrated to exhibit thisproperty in, e.g., N. Nakanishi et al, Scripta Metallurgica 5, 433-440(Pergamon Press 1971) and such materials may be doped to lower theirtransition temperatures to cryogenic regimes by known techniques.Similarly, 304 stainless steels have been shown to enjoy suchcharacteristics, E. Enami et al, id at pp. 663-68. These disclosures aresimilarly incorporated herein by reference.

British Patent Specifications Nos. 1,327,441 and 1,327,442 describe howthis property of heat recoverability can be used to fabricatecompression sleeves (i.e. tubular articles in which the forces of heatrecovery are directed radially inwardly) useful in joining cylindricalsubstrates such as hydraulic lines and other conduitry employed inaerospace applications. In the fabrication of these and other suchrecoverable couplings, the couplings are cooled below their transitiontemperature, for example by immersion in liquid nitrogen, and arediametrally expanded by forcing a mandrel through them, the mandreltapering outwardly to a transverse dimension greater than the originalinternal diameter of the coupling.

In monolithic heat recoverable metallic couplings of this type, theinterior surface of the coupling is machined prior to diametralexpansion in order to provide circumferential teeth which "bite" into orotherwise deform the surface of a substrate about which the coupling issubsequently heat recovered, enhancing the ability of the resultingarticle to resist tensile stress and, in particular instances, toachieve a gas-tight interface between coupling and substrate (as usedherein, the term "gas-tight" signifies the ability of acoupling-substrate interface as is found in a pipe joint to pass notmore than one bubble per minute over a five minute period when anarticle pressurized with nitrogen at 3000 psig is immersed in water).

Various problems arise from the provision of such teeth on the interiorsurface of monolithic heat recoverable metallic couplings. First of all,the teeth are subjected to enormous local pressures during mandrelexpansion, with consequent damage to the teeth frequently sufficientlysevere as (a) to impair the ability of the coupling to form a gas-tightjoint, (b) to reduce the tensile strength of the joint and (c) to lowerthe amount of pressure the joint is capable of withstanding. Secondly,many metallic materials susceptible to the impartaton of heatrecoverability are difficult to machine.

Other problems have arisen from the monolithic nature of couplingsheretofore employed. For one, such couplings tend to recover prematurelywhen placed over a warm substrate, requiring the use of special chillingtools to abate recovery prior to proper positioning of the coupling onthe substrate. Furthermore, rigid quality control procedures have beenrequired to ensure that, prior to application, any lubricant depositedon the interior surface of the coupling to aid mandrel expansion hasbeen removed. Finally, the somewhat limited range of materialssusceptible to the impartation of heat recoverability has, in certaininstances, prevented the optimum pairing of compression sleeve andsubstrate materials from mechanical, chemical and electrical standpointssuch, for example, as corrosion compatibility, thermal expansionproperties, creep resistance, sealability, compatibility of elasticmodulus and high temperature strength.

SUMMARY OF THE INVENTION

The present invention provides a device comprising a first, heatshrinkable or heat expansible member made from a memory metal and asecond, sleeve member positioned respectively inside or outside saidfirst member, said second sleeve member having such configuration that,and/or being made from such a material that it facilitates the formationof a secure coupling between the device and a substrate.

The present invention also provides a set of parts for making a deviceas described above which comprises a heat shrinkable or heat expansiblemember made from a memory metal and a sleeve member adapted to bepositioned respectively inside or outside the memory metal member.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view, partly in section, showing one manner of making acoupling device according to the present invention having an insertprovided with a plurality of teeth;

FIG. 2a shows, in cross-section, a heat recoverable coupling deviceformed in the manner shown in FIG. 1 and positioned about the alignedends of two pipes;

FIG. 2b shows the coupling device of FIG. 2a after recovery;

FIG. 3a shows, in cross-section, a second form of coupling deviceaccording to the present invention positioned about the aligned ends oftwo pipes;

FIG. 3b shows the coupling device of FIG. 3a after recovery;

FIG. 4a shows, in cross-section, a third form of coupling deviceaccording to the present invention positioned about the aligned ends oftwo pipes;

FIG. 4b shows the coupling device of FIG. 4a after recovery;

FIG. 5 is a view, partly in section, showing one manner for making acoupling device according to the present invention in which the insertis a simple gall-prone tube;

FIG. 6a shows the coupling device formed in the manner shown in FIG. 5positioned about the aligned ends of two pipes;

FIG. 6b shws the coupling device of FIG. 6a after recovery;

FIG. 7a shows a further form of heat recoverable coupling according tothe present invention positioned about the aligned ends of two pipes;

FIG. 7b shows the coupling device of FIG. 7a after recovery;

FIG. 8a shows a further form of device according to the presentinvention positioned about the aligned ends of two pipes;

FIG. 8b shows the device of FIG. 8a after recovery;

FIG. 9a shows a heat expansible device according to the presentinvention positioned within the aligned ends of two pipes;

FIG. 9b shows the device of FIG. 9a after recovery;

FIG. 9c shows a version of the heat-expandable device of FIG. 9apositioned within the aligned ends of two pipes;

FIG. 10 shows an insert sleeve suitable for use in the presentinvention;

FIG. 11a shows a further form of insert sleeve suitable for use in thepresent invention;

FIG. 11b shows, in cross-section, a device according to the presentinvention employing the insert sleeve of FIG. 11a after recovery aboutthe aligned end of two pipes;

FIG. 12 shows a further form of insert sleeve suitable for use in thepresent invention;

FIG. 13a shows a further for of insert sleeve according to the presentinvention;

FIG. 13b show, in cross-section, a device according to the presentinvention employing the insert sleeve of FIG. 13a;

FIG. 14a shows a further heat expansible device in the form of a rivet;

FIG. 14b shows the rivet of FIG. 14a after recovery;

FIG. 15a shows a further form of insert sleeve suitable for use in thepresent invention;

FIG. 15b is a longitudinal cross-section through FIG. 15a;

FIG. 16 shows a further form of insert sleeve for use in the presentinvention;

FIG. 17a shows a further form of insert sleeve for use in the presentinvention;

FIG. 17b shows an auxiliary insert member for use with the sleeve of17a;

FIG. 17c is a longitudinal section through FIG. 17b;

FIG. 18a shows a further form of insert sleeve for use in the presentinvention;

FIG. 18b is a cross-section through the mid-section of FIG. 18a;

FIG. 18c shows an auxiliary insert ring for use with the sleeve of FIG.18a;

FIG. 18d is a partical section showing the sleeve of FIG. 18a and thering of FIG. 18c;

FIG. 18e is a longitudial section through FIG. 18a;

FIG. 19 shows a further insert sleeve for use in the present invention;

FIG. 20 shows an auxiliary insert member for use with the sleeve fo FIG.19;

FIG. 21 illustrates a composite coupling device having a driver of largediameter;

FIGS. 22a-22g illustrate a composite coupling having a slit driver;

FIG. 23 illustrates a coupling wherein the driver has "z" shaped bends;

FIGS. 24a-24b illustrates another coupling device in which the driverhas "s" shaped convolutions;

FIGS. 25a-25b illustrate another coupling device having a convoluteddriver; and

FIG. 26 illustrates a composite coupling of yet another type in whichthe driver is a spring-like member.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is especially applicable to hollow, heatshrinkable members made from a memory metal, especially tubular members.The word "tubular" as used herein is not limited to right cylindricalhollow members, but also includes members of irregular and/or of varyingcross-section as well as, for example, Y-shaped, T-shaped and X-shapedmembers. An especially preferred member is a tubular heat shrinkablecompression coupling sleeve.

In such devices the second sleeve member is an insert member which ispreferably snugly positioned within the heat shrinkable memory metalmember, for example a tubular insert snugly positioned within a tubularcompression coupling sleeve and coaxially, e.g. concentrically, arrangedtherein.

However, in other useful devices according to the present invention thememory metal member is heat expansible, e.g. is a rod or tube, in whichcase the second sleeve member is preferably snugly positioned about saidmemory metal member. Such devices may be used, for example, in theinternal coupling of pipe lines.

The sleeve member may be formed as an integral part, for example as atube, but the present invention is not limited to such parts, forexample split cylinders, (the word "cylinder" being used in the generalsense and not being limited to a circular cross-section) and othershaped parts may in some cases be used to advantage. It will beappreciated from the discussion hereinafter that all that is necessaryis that the sleeve member covers at least a substantial part of thesurface of the memory metal member which would otherwise come intodirect contact with a substrate during coupling.

The sleeve member is preferably sized and configured so that it isalerted in at least one of its dimensions upon recovery of the heatrecoverable member and so that the change in its dimension(s) causes itsecurely to engage a substrate.

In one preferred embodimentof the present invention the sleeve member isprovided on at least one of its principal surfaces with means foreffecting a secure, and preferably gas-tight, seal between the deviceand a substrate upon recovery of the device. Such means preferablycomprises at least one tooth on said principal surface. Referring to thepreferred tubular forms of the device the tooth is preferably radiallydisposed and is more preferably formed circumferentially about thelongitudinal axis of said sleeve. Advantageously the sleeve is providedwith a plurality of teeth on each side of its mid-point.

However, alternative means may be employed to provide a good seal, forexample the sleeve may be provided with a ring of a deformable materialsuch as annealed aluminium or copper or may be coated with, for example,a fluorocarbon or another polymeric material or may be plated with areadily deformable metal.

The sleeve can advantageously be provided with such means on each of itsprincipal surfaces to ensure good contact both between itself and theheat recoverable metal member and between the coupling device and asubstrate, for example each of its principal surfaces may be providedwith one or more teeth and, preferably, each is provided with aplurality of teeth on each side of its mid-point. Advantageously suchteeth may be arranged in pairs, one member of which is formed externallyof the sleeve and the other of which is formed internally of the sleeve.Of course the number, shape and location of the teeth will varydepending upon the materials from which the teeth and the substrate areformed and upon the type of engagement which is desired between them.

In another preferred embodiment of the present invention the sleeve hasat least one weakened wall section, preferably at least a pair ofweakened wall sections. For example, the weakened sections may be slotsin the wall or may be "flats", i.e. areas on the surface of the insertsleeve where the wall thickness has been locally reduced, preferablyslots and flats are disposed parallel to the axis of the insert sleeveand pairs of slots or flats are preferably arranged symmetrically sothat relatively uniform deformation of the insert about itscircumference occurs upon its recovery. Preferably the slots and flatsare equidistant from the ends of the insert sleeve and it isadvantageous to provide at least two pairs of slots of flats on eitherside of, and equidistant from, a non-weakened mid-section. The flats arepreferably formed on the exterior surface of an insert sleeve.

In another preferred form of weakened insert sleeve the outside surfacethereof tapes from a maximum wall thickness at points adjacent to eitherend to a minimum at about its mid-section, the internal surface of theinsert sleeve being preferably uniform.

In all the above cases it may be preferable to provide the surfacesofthe insert sleeve, especially the interior surface, with a plurality ofteeth, as described above, preferably on either side of its mid-section.Alternatively, or additionally, it may also be preferable to form theinsert sleeve from a gall-prone material as described below.

In another preferred embodiment of the present invention the sleeve isfabricated from a gall-prone material, e.g., a metal. "Galling" hasreference to that condition arising from the affinity of gall-pronemetals, one from the other, which occasions seizure at the rubbingsurfaces of articles formed from those metals over and above normalfrictional effects, as by localized welding, followed by subsequentspalling and the creation of increased surface asperity. Cf. MetalsHandbook Vol. 1, p. 18, American Society for Metals, 8th ed. (1961). (Asused herein, the term "metal" unless otherwise qualified includes bothpure and alloyed metals). Gall-prone metals may gall one another and maygall other metals similar in hardness, surface characteristics andchemical make-up as well. Especially gall-prone metals include titanium,aluminium, magnesium and zirconium, and the inserts of the invention maybe formed of such metals. A preferred insert is formed of commerciallypure titanium, e.g. titanium 50A. One suitable titanium alloy is thatdesignated Ti-3Al-2.5 V, a titanium-aluminum-vanadium alloy. Preferredaluminium inserts are forme of the 6061 aluminium series, preferably6061 T6 aluminium. Those alloys comprise about 1% magnesium, 0.06%silicon, 0.25% copper and 0.25% chromium, the balance being aluminium.Other suitable materials for the insert include commercially purezirconium, Zircalloy 2 (containing about 1.5% tin, 0.12% iron, 0.1%Chromium, 0.005% nickel, the balance being zirconium), an alloyavailable from Zirconium Tech, Corp., Albany, Oreg.; and magnesiumalloys available from, e.g. Dow Chemical Corporation under thedesignations AZ 31 B-F (containing about 2.5-3.5% aluminium, 0.7-1.3%zinc, 0.2% manganese minimum, the balance being magnesium) and ZK 60A-T5 (containing about 4.8-6.2% zinc, 0.45% zirconium, the balance beingmagnesium).

For example, in some cases, the sleeve may be a simple tubular sleeveformed from a gall-prone metal, and no other means need be provided forensuring a good seal either between the sleeve and the heat recoverablemember or between the sleeve and a substrate. When other means areprovided on the sleeve (such as those described above) for effecting agood seal, but said means are provided only on one principal surface ofthe sleeve, it will again be advantageous in many cases to form thesleeve from a gall-prone material. In short, when the contactingsurfaces at either the interface between the sleeve and a substrate areboth substantially uniform it will be advantageous to form the sleevefrom a gall-prone material. It will be appreciated that, for optimalattainment of the advantages conferred by the use of gall-pronematerials the surface roughness of the sleeve will desirably be similarto that of one or more of the surfaces it contacts in any particularapplication. For example, for the hydraulic conduitry for which thedevices are employed the generally uniform surface of the sleeve willadvantageously exhibit a profilometer roughness of not more than about125 micro-inches, preferably not more than 63 micro-inches.

It shouls be appreciated from the above discussions that the dimensions,configuration and material of the sleeve member will be chosen foreffective performance having regard to the nature of theheat-recoverable metal member, the substrate and the environment inwhich the device of the present invention is to be used. Thus whilst theabove discussion has especially been directed to the provision of teethon the insert, to the provision of weakened sections in the insert andto the formation of the insert from gall-prone materials, it must bemade clear that a given insert may combine any two or all three of thesefeatures and indeed may include further design aspects and/or materialswhich will ameliorate its performance in any given application.

For example, the sleeve may be provided with a coating of a polymermaterial or a deformable metal, as described above, e.g. to facilitatethe formation of a gas-tight seal on recovery. Furthermore, the insertmay be provided with teeth and/or weakened portions only in certainparts of its structure.

In certain embodiments of the present invention the sleeve is itselfprovided with an insert or external auxiliary member, or both to enhanceits overall performance. Particular instances in which this may beadvantageous is when the compatibility requirements between the sleeveand the heat recoverable metal member differ from those between thesleeve and the substrate or when, as for example in the formation of afluid proof coupling between two hydraulic pipe substrates, the variousparts of the sleeve may be required to fulfil two different functions,e.g. proper mechanical coupling with the pipes and the formation of acorrosion-resistant seal at the junction between the pipes.

Thus, for example, it may be appropriate to provide the mid-section ofan insert sleeve having hard teeth on its interior surface with aseparate sealing ring insert at its mid-section to provide asatisfactory, e.g. corrosion-resistant and gas-tight, seal. Conversely,it may be appropriate to provide an insert sleeve having a generallysmooth corrosion resistant surface with one or more toothed insertmembers positioned away from its mid-point. Equally it may in some casesprove advantageous to provide an insert sleeve having overallcompatibility with the heat recoverable metal member with inserts bothfor corrosion-proof sealing purposes and for proper mechanical couplingwith the substrate(s). (It will be appreciated that there concepts applyalso to exterior sleeve members and also to compatibility with, andsatisfactory mechanical coupling to, the heat recoverable metal member).

The sleeve member may be provided with grooves or other recessed orotherwise shaped portions for the proper positioning of these furtherauxiliary insert (or external) members. Furthermore, the sleeve and/orthe auxiliary insert members may be made resilient to facilitate securepositioning.

When an insert sleeve is to be provided with such further auxiliaryinsert members it may be advantageous to provide it with slots, or toform it as a longitudinally split sleeve, so that said further auxiliaryinsert members can be inserted through said slots or through the slit toplace them in position. However, this will not be essential in allcases, for example, it may be possible to push the auxiliary insertmembers into the sleeve from one of the ends thereof.

It should also be appreciated that, whilst the present invention isespecially directed to avoiding the disadvantages present in some caseswhen the heat recoverable metal member is provided with teeth, theproblems sometimes associated with the provision of teeth, for example,difficulty in machining and deformation of the teeth during deformatione.g. mandrel expansion, will not always be significant. For example,some heat recoverable alloys are relatively easy to machine and, incertain applications, some deformation of the teeth during deformationwill not be serious. Furthermore, the provision of such teeth willsometimes be positively advantageous. Accordingly, it should be madeclear that the present invention also includes devices in which the heatrecoverable member is provided with means e.g. teeth on one or both ofits principal surfaces and is not limited to smooth-surfaced recoverabledrivers.

In the preferred tubular devices of the present invention the length ofthe sleeve can be greater than, equal to or less than the length L ofthe heat recoverable, e.g. heat shrinkable, member. Preferably, however,the sleeve protrudes from each end of the heat recoverable member so asto afford strain relief adjacent the opposite ends of the recoveredmember. In such a case the length of the sleeve is preferably notgreater than about L+2D_(i), or L+2D_(e), where D_(i) is the internaldiameter of the heat-shrinkable member and D_(e) is the externaldiameter of the heat-expansible member, and is more preferably notgreater than about L+D_(i) or L+D_(e).

It will be appreciated that the sleeve, e.g. the insert, of the deviceis preferably metallic. However, other materials having metal likeproperties and which are strictly speaking non-metallic, such asgraphite, graphite and glass composite may also be used in certainapplications. Suitable materials are well known and can easily beselected by those skilled in the art.

In the preferred use of the composite devices of the present inventionin effecting joints between adjoining lengths of hydraulic or othertubing formed, for example, from stainless steel, titanium or aluminum,the sleeve is preferably made from a metal comprising a major proportionof titanium. Titanium inserts are especially preferred when thesubstrate is made from stainless steel, e.g. 21-6-9(21% chromium, 6%nickel, 9% manganese) stainless steel. When the substrate is made from ahighly gall-prone metal the insert sleeve can be made from a lessgall-prone metal which, when brought into contact with the substratewill result in galling. For example, when the substrate is titanium theinsert may be stainless steel.

The preferred metals for use in the heat recoverable member includeequiatomic titanium-nickel alloys and, especially, the substitutedternary alloys described in U.S. Pat. Nos. 3,759,552 and 3,753,700.

Those skilled in the art will readily be able to select suitabledimensions for the coupling devices according to the present invention.However, by way of illustration, the relevant dimensions of anespecially preferred heat shrinkable coupling which can be used inadjoining 1/2 inch nominal O.D. tubing are given in the table below:

    ______________________________________                                        Parameter             Dimension (inch)                                        ______________________________________                                        heat shrinkable sleeve length                                                                       1.75                                                    heat shrinkable sleeve outer diameter                                                               .75                                                     insert sleeve length  2.00                                                    insert sleeve internal diameter                                                                     .508                                                    insert sleeve wall thickness                                                                        .036                                                    insert sleeve outer diameter                                                                        .580                                                    heat shrinkable sleeve inner diameter                                                               .534                                                    ______________________________________                                    

It will be appreciated that the present invention substantially solvesall the disadvantages of the heat recoverable metal coupling devicespreviously employed. The interposition of the sleeve between the heatrecoverable member and a substrate about which it is ultimatelyrecovered prevents substrate contamination by various residues such aslubricants which are sometimes present on the interior surface of acompression coupling member and admits the pairing of insert sleeve andsubstrate materials for compatibility from mechanical, and chemicalstandpoints such as corrosion, thermal expansion, creep resistance,sealability, elastic modulus, flexural characteristics and hightemperature strength. Any teeth that are provided in the couplingdevices may be formed on the insert sleeve and because of this they arenot exposed to the damaging forces involved in mandrel expansion.Because the heat recoverable member need have no teeth the manner inwhich it is expanded can be simplified, e.g. by bead or ball expansionas opposed to mandrel expansion. Additionally, in place of the taperedends previously provided on monolithic compression sleeves for strainrelief, the insert sleeves of the present invention may be made toprotrude from the opposite ends of the compression sleeve by asufficient amount to impart appreciable strain relief to the jointsformed on recovery. This again simplifies the manufacture of thecompression sleeves which can accordingly be formed from smaller machineblanks with consequent saving of expensive metal. Furthermore the insertsleeve act to insulate the chilled compression sleeves from warmsubstrates for a time sufficient to avoid premature recovery so that itis no longer necessary to resort to the chilling tools and othertechniques previously used.

It will also be appreciated that, whilst the foregoing description hasemphasised devices comprising a heat recoverable tubular sleeve havingan internal insert sleeve, the present invention is not limited to suchstructures. For example, the heat recoverable member, which in itsbroadest sense may be referred to as a "driver", i.e. a member whichupon recovery drives the other member of the composite device in thedirection of recovery, may be positioned internally of said other memberso as to force it outwardly rather than inwardly. In such cases thedriver may be solid as well as hollow.

Similarly, although the use of teeth is especially advantageous in manycoupling devices according to the present invention, it must be stressedthat by forming the insert sleeve from a gall-prone material the abilityof joints formed to resist tensile stresses can be markedly enhanced.Indeed, in particular cases, it has been found that resistance totensile stress is greater where gall-prone inserts having uniformsurfaces have been employed than where inserts are provided with aplurality of circumferential teeth which bite into or otherwise deformthe substrates.

In addition, apart from the uses of the devices of the present inventionin joining cylindrical substrates, as described in some detail above,they may be used to plug holes, either from an internal or an outwarddirection, to plug the ends of tubular conduits, either by means of acap type structure which has one solid end and one open end or by meansof a solid plug which expands outwards, and as rivets. One suitable wayof making a rivet in accordance with the present invention would be tohollow out the stem of a conventional rivet and to place within it adriver capable of expansion upon heating. In such an application, atleast the stem of the rivet will desirably be fabricated from agall-prone material.

Referring now to FIG. 1, an expansible cylindrical sleeve blank 10 restson a collar support 11, which is in turn replaceably supported in anannular recess in a platform 12. Frame members 13 suspend this assemblyin a suitable cryogenic fluid 14 such as liquid nitrogen so that sleeveblank 10 is entirely immersed therein. A tapered expansion mandrel 15 isdisposed within part 10 so as to position the upper portion or ramp 16of the mandrel 15 above the blank. The leading end of a pusher rod 17 isreceived in a recess 18 in the rear end of mandrel 15, the rear end ofrod 17 being detachably mounted on the forward end 19 of a hydraulicallypowered ram. Upon ram activation, mandrel 15 is forced downwardly by theaxial force imposed thereon by rod 17, expanding sleeve blank 10 to aninternal diameter equal to the greatest transverse dimension of mandrel15. In the course of the progressive expansion of blank 10 by mandrel15, those portions of the expanded blank 10 past which the mandrel hastravelled tend to spring back to a slight degree sufficient to engagethe exterior surface of an insert member 20 which is carried by rod 17into the sleeve blank 10. Typically, the greatest transverse dimensionof the mandrel is from 6% to 9% greater than the unexpanded innerdiameter of the sleeve blank 10. Following expansion, the retaineddiametral increase is commonly of the order of from 5 to 7%. Forexample, in the case of an unexpanded sleeve blank having an internaldiameter of 0.534 inch expanded with a mandrel whose greatest transversedimension is 0.593 inch, the expanded compression sleeve may spring back0.013 inch once the mandrel has passed through the expanded blank,engaging an insert having an outer diameter 0.580 in a snug, push fit.

Pusher rod 17 is sized to drop through the insert-supplied compressionsleeve once mandrel 15 has passed therethrough.

Of course, other means of supplying the insert to the expandedcompression sleeve will be apparent to those skilled in the art. Forexample, the insert can simply be manually supplied to the sleeve justprior to or in the course of substrate joinder with the coupling.

FIG. 2a depicts the composite coupling arising from anexpansion-assembly procedure as described with reference to FIG. 1positioned about the adjacent ends of end-to-end aligned tubularsubstrates 21 and 22, while FIG. 2b illustrates the assembly resultingfrom recovery of the composite of FIG. 2a about the so-alignedsubstrates. Preferably, as in the case of each of the compressionsleeves depicted in the drawings, the surface of heat recoverable sleevewhich contacts the insert is generally uniform, i.e. essentially devoidof discontinuous design features such as teeth. In the case of FIG. 2,the exterior principal surface of insert 20 is generally uniform whilethe interior principal surface bears plural, spaced apart teeth 23bounding the interior mid-section of the coupling 20. The wall thicknessof the body portion of insert 20 from which the teeth 23 depend ispreferably thinner than the wall thickness of compression sleeve 10 andis most preferably as thin as possible for maximum transmission ofrecovery forces. As appears from FIG. 2b, recovery of sleeve 10 causesteeth 23 to deform substrates 21 and 22, enhancing the resistance of theformed joint to tensile stress.

As those skilled in the art will realize, not every configuration ofcircumferential tooth is suited to formation of a gas-tight seal in thepractice of this invention. However, generally squared teeth such asthose depicted as formed on the interior surface of insert 20 in FIG. 2amay usefully be employed in increasing resistance to gas leakage.However, more knife-edged teeth are generally superior in this regard.

FIGS. 3a and 3b depict a further composite coupling formed according tothe present invention prior to and following its heat recovery about theadjacent ends of end-aligned tubular substrates 24 and 25. Of the twoprincipal surfaces of insert 26, the interior surface is generallyuniform, while the exterior surface bears plural radical teeth 27 whichmay or may not be circumferentially formed about the entirety of theinsert. As appears from FIG. 3b, recovery of the compression sleeveoccasions contiguous wave form generation in the insert and substratetubing, resulting again in enhanced resistance in the formed joint totensile stress.

In the case of each of the composite couplings of FIGS. 2 and 3 whereina principal surface of the insert is generally uniform, advantage may bederived by ensuring that the insert is formed of a gall-prone metal.

FIGS. 4a and 4b depict a further composite coupling formed according tothe present invention, before and after its recovery about the adjacentends of end-aligned tubular substrates 28 and 29. In FIG. 4a, both theinterior and exterior principal surfaces of the insert are generallyuniform; advantage may be derived by ensuring that the insert is formedof a gall-prone metal.

FIGS. 4a and 4b depict a further composite coupling formed according tothe present invention, before and after its recovery about the adjacentends of end-aligned tubular substrates 28 and 29. In FIG. 4a, both theinterior and exterior principal surfaces of insert 30 bear radial(preferably circumferential) teeth. Preferably, for maximum transmissionof recovery of forces to the substrate, individual ones of pairs of theteeth on insert 30 respectively protrude inwardly and outwardly from thebody of the insert at points equidistant from its mid-section. See, forexample, the teeth of pair 31-32 in FIG. 4a. FIG. 4b depicts the jointformed upon recovery of the composite coupling of FIG. 4a.

FIG. 5 shows a manner of making a composite coupling device similar tothat shown in FIG. 1, except that the heat-shrinkable sleeve is formedfrom a blank 40 and the insert sleeve 50 is made from a gall-pronemetal. The method of procedure and the relevant dimensions are otherwiseas described with reference to FIG. 1.

FIG. 6a depicts the composite coupling arising from anexpansion-assembly procedure like that depicted in FIG. 5 positionedabout the adjacent ends of end-to-end aligned tubular substrates 51 and52, while FIG. 6b illustrates the assembly resulting from recovery ofthe composite of FIG. 6b about the so-aligned substrates. In the case ofthe assembly of FIG. 6a formation of insert 50 from a gall-prone metalenhances resistance of the formed joint to tensile stress andadditionally assists in tensile load transfer through recovered sleeve40. That surface of the heat recoverable sleeve which contacts theinsert is preferably generally uniform i.e. essentially devoid ofdiscontinuous design features such as teeth, etc. For optimal attainmentof the advantage conferred by the use of gall-prone inserts, the surfaceroughness of the insert is desirably made like that of one or more ofthe surfaces it adjoins in the particular application. For example, forthe hydraulic conduitry for which the composite couplings are preferablyemployed, the generally uniform surface of the insert preferablyexhibits profilometer roughness not greater than about 63 micro-inches.

In applications in which a gas-tight joint is specified, the insertpreferably bears on its interior surface means for effecting a gas-tightseal between the exterior environment and the interior of the recovered,composite coupling. In FIG. 7a, compression sleeve 53 is supplied withan insert 54 having a mid-section 55 bounded by spaced apartcircumferential teeth 56 and 57, which are configured to effect agas-tight seal following recovery about a substrate. Thus, in FIG. 7b,recovered sleeve 53 is shown as having, in the course of recovery, tohave caused teeth 56 and 57 to, in effect, incise the tubular substrates58 and 59. Appropriately configured teeth, by deforming the substrate,by themselves deforming during recovery, or by a combination of both canbe employed to ensure gas-tightness of the completed joint. Of course,alternative methods may serve as well. For example, a portion of theinsert on either side of the interior mid-section thereof may bear aring of a deformable material such as annealed aluminium or copper, becoated with, e.g. a fluorocarbon or other polymeric material, be platedwith a readily deformable metal or otherwise be provided with means foreffecting a gas-tight seal upon recovery.

The foregoing description has emphasized devices wherein the insert hasone or more teeth on one or both of its principal surfaces in order toimprove the properties of the heat recovered article or devices on whichthe insert sleeve is made from a gall-prone metal.

The following FIGS. 8a to 13b illustrate how advantages can be obtainedby forming the insert with a weakened wall section. The weakeningfacilitates selective collapse of the insert upon heat recovery of thecompression sleeve with a concomitant selective regulation of thecompressive forces transmitted to the substrate.

FIGS. 8a and 8b depict a further composite coupling formed according tothis invention, respectively before and after its recovery about theadjacent ends of end-aligned tubular substrates 63 and 64. Of the twoprincipal surfaces of insert 65, the interior surface is generallyuniform, while the exterior surface has a uniform taper from a maximumwall thickness at about its mid-point 66 giving it an hourglassconfiguration. As appears from FIG. 8b, recovery of the compressionsleeve occasions a deformation of the insert so that it exerts greatercompressive forces on the substrate at a point near the end of theinsert than at its mid-point. This differential causes the insert andsubstrate to deform as shown in FIG. 8b resulting in enhanced resistancein the formed joint to tensile stress.

FIGS. 9a and 9b depict a somewhat similar further composite couplingformed according to this invention wherein the heat recoverable memberor driver is positioned internally of the other member. In FIG. 9a, theend-aligned substrates, are positioned about tubular member 69 whichitself is positioned around heat recoverable member 70. Of the twoprincipal surfaces of tubular member 69, the exterior surface isgenerally uniform, while the interior surface tapers uniformly from amaximum wall thickness at points at or near its ends to a minimum wallthickness at about its mid-point 71. Upon heat recovery of member 70,deformation of the insert and the substrate occurs as shown in 9bresulting in enhanced resistance in the formed joint to tensile stress.Coupling devices of this type are particularly useful when it is desiredto couple substrates where an exterior coupling would not be useablebecause of the spare requirements of the environment of the coupling.Heat recoverable member 70 is shown as a solid rod. However, a tubulardriver can be used where necessary to provide a pathway for fluids.

Inserts of this invention with a weakened wall section are also obtainedby forming the insert with one or more slots or elongate flats. A flatis an area in the exterior surface of the insert where the wallthickness has been locally reduced. Preferably the slots and flats aredisposed parallel to the longitudinal axis of the insert. Normally, atleast one pair of slots or flats are employed in an arrangement wherebyrelatively uniform deformation of the insert about its circumferenceoccurs, for example by symmetrical arrangement.

FIG. 9c shows a composite coupling formed according to this inventionsimilar to that shown in FIGS. 9a and 9b. In FIG. 9c, end-alignedsubstrates 67' and 68' are positioned about a tubular member 69' whichitself is positioned around heat-recoverable member 70'. Of the twoprincipal surfaces of tubular member 69', the exterior surface isgenerally uniform, while the interior surface has a plurality of teeth72'.

Referring now to FIG. 10, there is shown in perspective tubular insert72 for a composite coupling formed according to this invention. Insert72 has weakened wall sections formed by a pair of slots 73 whose longdimension is parallel to the longitudinal axis of the insert. Themid-point of the slots corresponds to the mid-point of the insert, theirends being equidistant from the ends of the insert.

FIG. 11a is a perspective of a tubular insert 74, similar to that ofFIG. 10. However, in insert 74 the weakened wall sections are formed bya pair of elongate flats 75 parallel to the longitudinal axis of theinsert.

FIG. 11b depicts a cross-section of a composite coupling employing theinsert of FIG. 11 after its recovery about the adjacent ends ofend-aligned tubular substrates 76 and 77. The extent of deformation isexaggerated for purposes of illustration. As appears from FIG. 11b,weakening the insert by means of the flats results in greaterdeformation at the center of the coupling than would normally occur.This improves the interfacial pressure between the insert and thesubstrate thereby improving the pressure integrity of the coupling. Acoupling employing the insert of FIG. 10 would have, if shown, across-section similar to that of FIG. 11b.

FIG. 12 is a perspective of another tubular insert 78 useful in thecomposite couplings of this invention. Insert 78 has weakened wallsections formed by two pairs of slots 79 disposed on either side of anonweakened mid-section 80.

The insert 81 of FIG. 13a is similar to that of FIG. 12 except that theweakened wall sections are two pairs of elongate flats 82 disposed aboutthe non-weakened mid-section 83.

FIG. 13b depicts a cross-section of a composite coupling employing theinsert of FIG. 13a after its recovery about the adjacent ends ofend-aligned tubular substrates 84 and 85. The extent of deformation isexaggerated for purposes of illustration. As appears from FIG. 13bweakening the insert by means of the flats results in greaterdeformation of the insert and substrates at points intermediate the endsof the insert and its non-weakened mid-section. This deformationenhances the resistance of the formed joint to tensile stress.

Although the principal surfaces of the inserts of FIGS. 10-13 are shownas being generally uniform, either or both surfaces can be provided withteeth as hereinbefore discussed. Preferably, the inserts are providedwith a plurality of teeth on either side of the mid-section. Mostpreferably, the teeth are located on the inside surface of the inserts.The use of teeth further improves the resistance of the recoveredcoupling to tensile stress. Alternatively, or in addition, the insertscould be made from a gall-prone material as described above.

It will be apparent to those skilled in the art that the extent to whichthe insert is weakened determines the extent of its deformation whencompressed upon heat recovery of the compression sleeve. In the case ofthe slots, the extent of weakening is determined by the number, lengthand width of the slots. In the case of flats, the number, length andwidth of the flats as well as their depth determines the extent ofweakening.

While the foregoing description has emphasized devices comprising a heatrecoverable tubular sleeve having an internal insert, it is to beunderstood that the present invention is not limited to such structures.For example, the recoverable driver may be positioned internally of theother member, such that expansive recovery of the driver will force theother member outwardly rather than inwardly, In such cases, the drivermay be solid as well as a tubular sleeve.

A driver capable of expansive recovery is conveniently obtained bydrawing, by method's well known to the art, a solid or hollow rod, ofthe desired heat-stable diameter, while in its martensitic state to thedesired heat-recoverable diameter. Upon warming to a temperature inwhich it exists in its austenitic state, the rod contracts in lengthwith an expansion in diameter.

One example of such an application of the present invention is a rivetsuch as that shown in cross-section in FIG. 14a. Rivet 86 as shown has ahollow stem 87 forming a tubular section 88 for a heat recoverabledrivers 89. Preferably the hollow portion of the stem has a diameter atthe cap end greater than the diameter at its opening, the diameter atthe opening being such that the driver is easily inserted. FIG. 14b is across-section view of the rivet of FIG. 14a after heat recovery. A rivetof this type is particularly useful in those applications where blindrivets are employed.

The following figures illustrate various forms of the present inventionin which the insert sleeve is provided with a combination of featuressuch as those described above.

In FIG. 15a the insert sleeve 90 is provided with longitudinal terminalslots 91 on either side of its mid-section 92 and is also provided withinternal teeth 93 for enhancing the contact made by the insert sleevewith a substrate. As can be seen from FIG. 15b the teeth 93 extendbeyond the length equal to that of the slots 91. In the mid-section 92of the sleeve continuous teeth are provided for sealing purposes. Suchan insert sleeve can, for example, advantageously be made from acopper-nickel alloy.

FIG. 16 shows a similar sleeve 94 which is provided with a plurality ofslots 95 on either side of its mid-section. In this case, however, theslots do not extend to the ends of the sleeve. As in FIG. 15b, thesleeve can be provided with a plurality of teeth in the vicinity of theslots. Such a sleeve can be made, for example, from a copper-nickelalloy.

The following figures illustrate the provision of further auxiliaryinserts. In FIG. 17a there is shown a sleeve 100 which is provided withslots 101 in a manner similar to that in the sleeves of FIGS. 15a and16. However, in this case the sleeve is not itself provided withinternal teeth. Instead, there is provided an auxiliary insert member103 as shown in FIG. 17b. FIG. 17c shows, in cross-section, the internalconfiguration of the insert 103. The auxiliary insert 103 can be pushedinto the insert sleeve 100. As an alternative to the provision ofauxiliary member 103 the sleeve 100 may be provided with a series ofring segments the internal surfaces of which may be toothed or plain.These can be inserted into the insert sleeve 100 by pushing them in fromone or both ends. Alternatively, they may be inserted through the slots101 and then maneuvered into position. For this purpose it may beadvantageous to enlarge one or more of the slots 101 e.g. as shown inslot 102 in FIG. 17a.

It will be appreciated that, in some instances, it may be possible touse the further auxiliary members such for example as member 103 and toomit the main insert sleeve e.g. sleeve 100.

It will also be appreciated that the nature of the materials used forthe insert sleeve 100 and the further auxiliary members e.g. 103 can bechosen to ensure good compatability with the driver member and thesubstrate. In this manner, for example, tooth hardness and corrosioncompatability may be made independant variables in the choice of design.

FIG. 18a shows a further form of insert sleeve 104 provided with fourlongitudinal slots 105 one of which is widened to provide an enlargedcentral portion 106. FIG. 18b shows a cross-section through this centralportion and FIG. 18e shows a section through the length of insert sleeve104 from which it will be seen that the sleeve is provided with teeth107 on either side of its mid-section 108. In order to provide a goodseal about, for example, two pipes abutting in the region of itsmid-section a further auxiliary sealing ring 109 made, for example, froma copper-nickel alloy can be positioned within the mid-section 108 ofthe sleeve 104. This can be achieved by inserting the ring 109 throughthe enlarged portion 106 of one of the longitudinal slots 105 and thentwisting the ring through 90° and maneuvering it into position. Themid-section 108 of the sleeve 104 may be internally recessed 110 tofacilitate correct positioning of the ring 109. This is shown in FIG.18d.

FIG. 19 shows yet a further form of insert sleeve 111 which is providedwith four large longitudinal slots 112 so that, in effect, the insertsleeve forms a cage. The object of this cage is to provide a casing forauxiliary insert members. For example the sleeve 111 could be made froma soft material which is compatible with hydraulic fluids and which iscapable of good contact with a heat recoverable metal driver. In thiscase it may be advantageous to insert a further auxiliary member 113 isprovided with external teeth 114 to facilitate secure contact with thesleeve 111 and is also provided with a central annular lug 115 which cancooperate with grooves 116 in the sleeve 111 to facilitate correctpositioning. The auxiliary member 113 can, of course, also be providedwith internal teeth for contacting a substrate. Preferably the portion115 is resilient so that it exerts a secure positioning pressure on thegrooves 116.

Alternatively, in other applications it may be advantageous to make thesleeve 111 itself toothed (or gall-prone) and resilient in which case acentral soft sealing ring such, for example, as ring 109 in FIG. 18c,may be positioned in the grooves 116 and held there by the spring forcesof the segments of the sleeve 111.

It will be appreciated from the above discussion that, whilst certainspecific insert sleeves and auxiliary members have been described, manyother variations will be possible according to the particularapplication desired.

A typical application for the composite couplings described above is tojoin tubular cylindrical substrates. Properly dimensioned, thesecouplings can be employed to join substrates that vary greatly in size.For example, they might find application in joining tubing sections thatcould be used for hydraulic systems in aircraft. They can also be usedto join sections of pipe of very large dimension.

Also as indicated above, the drivers associated with the compositecouplings described in the aforementioned Martin applications aregenerally tubular members. Composite couplings employing them arelimited by the amount of recoverable dimensioned change that can beimparted to the drivers which in the case of tubular drivers is on theorder of 6-8%.

Therefore, the present invention also provides composite couplings inwhich the driver is capable of undergoing a high percentage of recoverywhen compared to composite couplings in which the driver-insertcombination are simple tubular members.

One manner in which this is accomplished is to provide compositecouplings in which the driver is of relatively large diameter whencompared to that of the substrate. However, it is presently preferred toemploy as drivers, members that can undergo large dimensional change inthe process of being rendered heat recoverable by virtue of their beingprovided with structural characteristics that can undergo a bendingdeformation when compressive or tensioning forces are applied.

FIG. 21 illustrates a composite coupling according to the presentinvention in which a high percentage of recovery is obtained byemploying as a driver heat-shrinkable member 117 which has a very largediameter relative to the substrate 118. Insert 119 is also of largediameter but is provided with a plurality of rib members 120 whichtransmit the recovery force to the substrate. Preferably, insert 110 isprovided with slots 121 as shown in the FIG. 15a or otherwise weakenedto facilitate its deformation as the driver undergoes recovery.

By reference to FIG. 21 it can readily be seen that as the diameter ofthe driver is increased relative to that of the substrate, the totalamount of recovery that can potentially be exerted upon the substrate isincreased. Thus, if the diameter of driver 117 in its recoverable formis, for example, 4 times that of an expanded driver exactly sized toreceive the substrate its effective recovery is 24-32% (4 times 6-8%)rather than the usual 6-8%.

In FIGS. 22a·22g is illustrated a composite coupling in which the driver122 is capable of a high percentage of recovery from an expanded form bybeing provided with a plurality of slots 123 at both ends which allowthe ends to be expanded by bending the fingers 124 defined by thoseslots as shown in FIG. 22b. Center section 125 of the driver may also beexpanded, for example by using a mandrel, the usual 6-8%.

An assembled composite coupling prior to recovery employing driver 122is shown in FIG. 22c with cylindrical substrates 126 and 127 inserted inthe aperture defined by slotted insert 128. As shown, insert 128 isprovided with teeth to more securely engage the substrate. It may alsobe made of a metal that is gall-prone relative to the substrate. Aspreviously indicated, the slots facilitate the insert's deformation uponrecovery of the driver.

In the assembly shown in FIG. 22c, snap rings 129 are provided to assistin retaining the insert in the coupling prior to recovery and totransmit the recovery force at points intermediate the ends and centerof the coupling. The recovered composite is shown in FIG. 22d. Theconstriction imparted to the substrate, exaggerated in FIG. 22d forillustrative purposes, increases the tensile strength of the joint.

A modification of driver 122 is shown in FIG. 22e in which the fingers124 are provided with rounded interior surfaces 130 which perform afunction similar to the snap rings of FIG. 22c and 22d. Assembledcouplings before and after recovery employing modified driver 122 areshown in FIGS. 22f and 22g.

Another composite coupling capable of a high percentage of recovery isshown in FIG. 23 in which a tubular heat shrinkable driver 131 has beenprovided with a plurality of slits 132 that begin at one edge of thedriver but terminate just short of the other edge in a pattern in whichthe edge that is slit is alternated. As can be seen from FIG. 23, uponexpansion to impart heat recoverability, the tube is given a series of"z" shaped bends by virtue of angular deformation at the base of eachslit. The slits allow the driver to expand more than the usual 6-8% byreason of the binding made of deformation.

In FIG. 23, an insert member 133 has been inserted in the driver. Itwill be appreciated that it can be provided with teeth and/or be made ofa gall-prone metal. Also, it can be structurally weakened as byproviding it with slots to facilitate its deformation.

A composite coupling similar to that of FIG. 23 is shown in FIGS.24a-24b in which driver 134 is obtained by bending a metallic member,for example wire (preferably rectangular wire) to give it a series ofgenerally "s" shaped convolutions. The convolutions are arranged in amanner such that when installed upon the insert 135, a line bisectingthe angle defined by the convolutions lies generally parallel to thelongitudinal axis of the coupling. When expanded, the bent configurationof the driver allows its expansion to exceed the usual 6-8% as it canbend to increase its diameter. A coupling employing two such drivers isillustrated in FIG. 24b.

Yet another composite coupling ha;ving a convoluted driver is shown inFIGS. 25a-25b. In that coupling, heat recoverable driver 136 is providedwith convolutions perpendicular to the longitudinal axis of thecoupling. It has the advantage of being conveniently made to almost anylength by an extrusion process. Insert member 137 can be any of theusual structures employed in the composite couplings of this invention,i.e., it can have teeth or serrations or be gall-prone to improveengagement with the substrate and can be structurally weakened tofacilitate deformation. A driver like member 136 can easily becompressed to a smaller diameter to allow it to radially expand uponrecovery where such is useful. The percentage of recovery that can beexhibited by such drivers is increased by virtue of the fact thatbending is allowed by the convolutions.

As shown in FIG. 25b, convoluted driver 136 can be provided with anunyielding cylindrical jacket 138 which has the effect of focussing moreof the recovery force upon insert 137 and ultimately substrates 139 and140.

FIG. 26 illustrates another composite coupling according to the presentinvention. In this coupling, the driver compreses a generallycylindrical member 141 that has been made by joining the ends of aspringlike coil of metal wire. Preferably, a composite couplingemploying such a driver utilizes them in pairs as shown. To facilitatetheir use, insert 142 is shown with a pair of channels 143 and 144adapted to receive the coils. As shown in FIG. 26, the composite is usedto join flanged substrates 145 and 146 although it can also be employedto couple simple tubular or other cylindrical sections.

The couplings described herein are but illustrative of the many formesthe present invention may take. It will be apparent that the compositecouplings of this invention are suited to many applications where thejoining of hollow or solid cylindrical substrates is desired.

I claim:
 1. A composite device for securely engaging at least onesubstrate which comprises:(a) at least one tubular, heat-recoverable,metallic compression sleeve; and (b) at least one tubular, metallicinsert snugly and concentrically disposed within, adjacent to, and incontact with the compression sleeve so that when the compression sleeveis heat-recovered by being heated above its transition temperature, theinsert is altered in at least one of its dimensions and is driveninwardly by the heat-recovered sleeve for securely engaging and forminga gas-tight seal with the substrate.
 2. The device of claim 1 whereinthe insert is formed of a gall-prone metal and both principal surfacesof the insert are generally uniform.
 3. A composite device as claimed inclaim 1 whereinthe interior and exterior surfaces of the insert eachbear at least one radial tooth circumferentially formed about thelongitudinal axis of the insert, at least the tooth on the interiorsurface being continuous, wherein when the compression sleeve isheat-recovered by being heated above its transition temperature, theteeth remain on the respective surfaces and the insert is driveninwardly by the heat-recovered sleeve such that the tooth on theinterior surface of the insert securely engages and forms a gas-tightseal with the substrate.
 4. The device of claim 3 wherein both theinterior and exterior surfaces of the insert bear a plurality of theteeth, at least the teeth on the interior surface being continuous, theteeth being separate and longitudinally spaced apart from each other. 5.A device according to claim 4 wherein both principal surfaces of saidinsert bear a plurality of teeth on either side of the mid-sectionthereof.
 6. A device according to claim 5 wherein said teeth arearranged pairwise such that individual ones of pairs of said teethrespectively protrude inwardly and outwardly from the body of saidinsert at points equidistant from said mid-section.
 7. The deviceaccording to claim 1 wherein said insert has a plurality of ribsextending from its inner surface to contact the substrate and transmitthe forces caused by recovery of the compression sleeve.
 8. A deviceaccording to claim 1 wherein the compression sleeve has a plurality ofslots at either end radiating from a center section, said sleeve when inits recoverable configuration having a greater outside diameter at itsends than at its center section.
 9. A device according to claim 1wherein said compression sleeve has a plurality of slits that begin atone edge and terminate short of the other edge of the compressionsleeve, said beginning edge alternating between adjacent slits.
 10. Adevice according to claim 1 wherein said compression sleeve isconvoluted, said convolutions being parallel to the longitudinal axis ofthe composite device.
 11. A device according to claim 1 wherein thecompression sleeve is convoluted, said convolutions being perpendicularto the longitudinal axis of the composite device.
 12. A composite devicefor securely engaging at least one hollow tubular substrate whichcomprises:(a) at least one heat-recoverable metallic driver; and (b) atleast one tubular metallic sleeve snugly and concentrically disposedadjacent to, in contact with, and surrounding the exterior surface ofthe driver so that when the driver is heat-recovered by being heatedabove its transition temperature, the sleeve is altered in at least oneof its dimensions and is driven outwardly by the heat-recovered driverfor securely engaging and forming a gas-tight seal with the substrate.13. The device of claim 12 wherein both principal surfaces of the sleeveare generally uniform and the sleeve is formed of a gall-pone metal. 14.A composite device as claimed in claim 12 whereinthe interior surface ofthe tubular sleeve bears at least one radial tooth circumferentiallyformed about the longitudinal axis of the sleeve and the exteriorsurface of the sleeve is generally uniform, and wherein when the driveris heat-recovered by being heated above its transition temperature, thetooth remains on the interior surface of the sleeve.
 15. The device ofclaim 14 wherein the exterior surface of the sleeve has a profilometerroughness not greater than about 125 micro-inches.
 16. A deviceaccording to claim 15 wherein the sleeve is formed of a metal comprisinga major proportion of titanium and wherein the exterior surface of thesleeve exhibits profilometer roughness not greater than about 63micro-inches.
 17. The device of claim 12 wherein the sleeve has aweakened wall section.
 18. The device of claim 12 in which the sleevebears on it exterior surface at least one continuous radial toothcircumferentially formed about the longitudinal axis of the sleeve,wherein when the driver is heat-recovered the tooth remains on theexterior surface and securely engages and forms a gas-tight seal withthe substrate.
 19. The device of claim 18 in which the sleeve has aweakened wall section.
 20. A method for forming a connection to asubstrate comprising the steps of:(a) placing on the exterior of thesubstrate a composite device comprising (i) a tubular heat-recoverablemetallic compression sleeve and (ii) a tubular metallic insert snuglyand concentrically disposed within, adjacent to, and in contact with thecompression sleeve; and (b) heat-recovering the compression sleeve byheating the compression sleeve to above its transition temperature foraltering the insert in at least one of its dimensions and driving theinsert inwardly for securely engaging and forming a gas-tight seal withthe substrate.
 21. The method of claim 20 whereinthe composite device isplaced on a pair of substrates the insert is driven inwardly forsecurely engaging and forming a gas-tight seal with both substrates. 22.The method of claim 21 wherein the interior surface of the tubularmetallic insert bears at least two continuous radial teethcircumferentially formed about the longitudinal axis of the insert, theteeth being separate and longitudinally spaced apart from each other,wherein the step of heat-recovering the compression sleeve drives theteeth into the substrates for securely engaging and forming a gas-tightseal with both substrates.
 23. The method of claim 20 wherein theinterior surface of the tubular metallic insert bears at least onecontinuous radial tooth circumferentially formed about the longitudinalaxis of the insert, wherein the step of heat-recovering the compressionsleeve drives the tooth into the substrate for securely engaging andforming a gas-tight seal with the substrate.
 24. A method for forming aconnection to a hollow, tubular substrate which comprises the stepsof:(a) placing inside the substrate a composite device comprising (i) aheat-recoverable, metallic driver and (ii) a tubular metallic sleevesnugly and concentrically disposed adjacent to, in contact with, andsurrounding the exterior surface of the driver; and (b) heat-recoveringthe driver by heating the driver to a temperature above its transitiontemperature for altering the sleeve in at least one of its dimensionsand driving the sleeve outwardly for securely engaging and forming agas-tight seal with the substrate.
 25. A method as claimed in claim 24wherein the composite device is placed inside a pair of substrates, andthe step ofheat-recovering the driver comprises driving the sleeveoutwardly for securely engaging and forming a gas-tight seal with bothsubstrates.
 26. The method of claim 25 wherein the exterior surface ofthe tubular metallic sleeve bears at least two continuous radial teethcircumferentially formed about the longitudinal axis of the insert, theteeth being separate and longitudinally spaced apart from each other,wherein the step of heat-recovering the driver drives the teeth into thesubstrates for securely engaging and forming a gas-tight seal with bothsubstrates.
 27. The method of claim 24 wherein the exterior surface ofthe tubular metallic sleeve bears at least one continuous radial toothcircumferentially formed about the longitudinal axis of the insert,wherein the step of heat-recovering the driver drives the tooth into thesubstrate for securely engaging and forming a gas-tight seal with thesubstrate.
 28. A composite device for securely engaging at least onesubstrate which comprises:(a) a tubular, heat-recoverable, metalliccompression sleeve; and (b) a tubular, metallic insert, the interiorsurface of the insert bearing at least one continuous toothcircumferentially formed about the longitudinal axis of the insert, theexterior surface of the insert being generally uniform, the insert beingsnugly and concentrically disposed within, adjacent to, and in contactwith the compression sleeve, wherein when the compression sleeve isheat-recovered by being heated above its transition temperature, thetooth remains on the interior surface of the insert and the insert isaltered in at least one of its dimensions and is driven by theheat-recovered sleeve such that the tooth securely engages and forms agas-tight seal with the substrate.
 29. The device of claim 26 whereinthe interior surface of the insert bears a plurality of such teeth, theteeth being separate and longitudinally spaced apart from each other.30. A device according to claim 29 wherein the teeth are arrangedpairwise such that individual ones of pairs of the teeth protrudeinwardly from the body of the insert at points equidistant from themid-section.
 31. The device of claim 1 or 28 wherein the insert has aweakened wall section.
 32. The device of claim 31 wherein the insert hasat least one pair of weakened sections that are slots.
 33. The device ofclaim 31 wherein the insert has at least one pair of weakened sectionsthat are flats on the exterior surface of the insert.
 34. A compositecoupling for securely joining substrates which comprise:(a) a pluralityof tubular, heat-recoverable, metallic compression sleeves; and (b) ahollow metallic insert snugly and concentrically disposed within,adjacent to, and in contact with the compression sleeves so that wheneach compression sleeve is heat-recovered by being heated above itstransition temperature, the insert is altered in at least one of itsdimensions and is driven inwardly by the heat-recovered sleeve forsecurely engaging and forming a gas tight seal with at least one of thesubstrates.
 35. The coupling of claim 34 where a compression sleeve isdisposed near each end of the insert.
 36. The coupling of claim 34wherein the interior surface of the insert bears at least one continuoustooth circumferentially formed about the longitudinal axis of the insertand the tooth remains on the interior surface of the insert when theinsert is driven inwardly such that the tooth securely engages and formsa gas-tight seal with at least one of the substrates.
 37. The couplingof claim 36 wherein the interior surface of the insert bears a pluralityof such teeth, the teeth being separate and longitudinally spaced-apartfrom each other.
 38. A composite device for securely engaging at leastone substrate which comprises:(a) a tubular heat-recoverable, metalliccompression sleeve; and (b) a plurality of tubular metallic insertssnugly and concentrically disposed within, adjacent to, and in contactwith the compression sleeve so that when the compression sleeve isheat-recovered by being heated above its transition temperature, eachinsert is altered in at least one of its dimensions and is driveninwardly by the sleeve for securely engaging and forming a gas tightseal with the substrate.
 39. A composite device for securely engaging atleast one tubular substrate which comprises:(a) an external, hollow,heat-recoverable, metallic compression driver; (b) a tubular metallicinsert sleeve snugly and concentrically disposed within, adjacent to andin contact with the compression driver; and (c) at least one insertmember concentrically disposed within, adjacent to, and in contact withthe insert sleeve, the insert member being shorter than the insertsleeve; wherein the compression driver is heat-recovered by being heatedabove its transition temperature, the insert sleeve is altered in atleast one of its dimensions and is driven inwardly by the heat-recoveredsleeve for securely engaging and forming a gas-tight seal with thesubstrate by driving the insert member into the substrate.
 40. Thedevice of claim 39 comprising a plurality of insert members spaced apartfrom each other.
 41. The device of claim 40 in which the insert membersare toothed.
 42. The device of claim 41 in which the insert sleeve has agenerally smooth, corrosion resistant internal surface.
 43. A compositedevice for securely engaging a hollow tubular substrate whichcomprises:(a) a heat-recoverable, metallic driver; (b) a tubularmetallic intermediate sleeve concentrically disposed adjacent to, incontact with, and surrounding the exterior surface of the driver; and(c) at least one exterior sleeve concentrically disposed adjacent to, incontact with, and surrounding the exterior surface of the intermediatesleeve, the exterior sleeve being shorter than the intermediate sleeve;wherein when the driver is heat-recovered by being heated above itstransition temperature, the intermediate sleeve is altered in at leastone of its dimensions and is driven outwardly by the heat-recovereddriver for securely engaging and forming a gas tight seal with thesubstrate by driving the exterior sleeve into the substrate.
 44. Anassembly comprising:(a) a pair of substrates; (b) at least one tubular,metallic compression sleeve that has been heat-recovered by being heatedabove its transition temperature; and (c) at least one tubular, metallicinsert snugly and concentrically disposed within, adjacent to, and incontact with the interior surface of the compression sleeve and incontact with the exterior surface of both substrates, wherein when thecompression sleeve was heat-recovered by being heated above itstransition temperature, the insert was altered in at least one of itsdimensions and was driven inwardly by the heat-recovered sleeve forsecurely engaging and forming a gas-tight seal with both substrates. 45.The assembly of claim 44 wherein the insert is formed of a gall-pronemetal and both principal surfaces of the insert are essentially devoidof discontinuous design features such as teeth.
 46. The assembly ofclaim 44 wherein both the interior and exterior surfaces of the inserteach bears at least two radial teeth circumferentially formed about thelongitudinal axis of the insert, at least the teeth on the interiorsurface of the insert being continuous, the teeth on each surface beingseparate and longitudinally spaced apart from each other, wherein whenthe compression sleeve was heat-recovered by being heated above itstransition temperature, the insert was driven inwardly by the sleevesuch that the teeth on the inner surface securely engaged and formed agas-tight seal with both substrates.
 47. The assembly of claim 46wherein both the interior and exterior surfaces of the insert bear morethan two of such teeth, the teeth being separate and longitudinallyspaced apart from each other.
 48. The assembly of claim 47 wherein boththe interior and exterior surfaces of the insert bear a plurality ofteeth on either side of the mid-section thereof.
 49. The assembly ofclaim 46 wherein the teeth are arranged pairwise such that individualones of pairs of said teeth respectively protrude inwardly and outwardlyfrom the body of the insert at points equidistant from the midsection.50. The assembly of claim 44 wherein the insert has a weakened wallsection.
 51. The invention of claim 2 or 44 wherein both principalsurfaces of the insert exhibit a profilometer roughness not greater thanabout 125 micro-inches.
 52. An assembly comprising:(a) a pair of hollowsubstrates; (b) at least one metallic driver that has beenheat-recovered by being heated above its transition temperature; and (c)at least one tubular metallic sleeve snugly and concentrically disposedadjacent to, in contact with, and surrounding the exterior surface ofthe driver and in contact with the interior surface of both substrates,wherein when the driver was heat-recovered by being heated above itstransition temperature, the sleeve was altered in at least one of itsdimensions and was driven outwardly by the heat-recovered driver forsecurely engaging and forming a gas-tight seal with both substrates. 53.The assembly of claim 52 wherein both principal surfaces of the sleeveare essentially devoid of discontinuous design features such as teethand the sleeve is formed of a gall-prone metal.
 54. The invention ofclaim 13 or 53 wherein both principal surfaces of the sleeve exhibitprofilometer roughness not greater than about 125 micro-inches.
 55. Theassembly of claim 52 wherein the sleeve has a weakened wall section. 56.The invention of claim 12 or 52 wherein the sleeve extends beyond theopposite ends of the driver and is not greater in length than about thequantity L+2 De, where L is the length of the sleeve and De is itsexternal diameter.
 57. The invention of claim 12 or 52 wherein thedriver is a tubular sleeve.
 58. The invention of claim 12 or 52 whereinthe driver is a cylindrical rod.
 59. As assembly comprising:(a) a pairof substrates; (b) a tubular metallic compression sleeve that has beenheat-recovered by being heated above its transition temperature; and (c)a tubular, metallic insert, the interior surface of the insert bearingat least two continuous teeth circumferentially formed about thelongitudinal axis of the insert, the teeth being separate andlongitudinally spaced apart from ech other, the exterior surface of theinsert being essentially devoid of discontinuous design features such asteeth, the insert being snugly and concentrically disposed within,adjacent to, and in contact with the interior surface of the compressionsleeve and in contact with the exterior of both substrates, wherein whenthe compression sleeve was heat-recovered by being heated above itstransition temperature, the insert was altered in at least one of itsdimensions and was driven inwardly by the sleeve such that the teethsecurely engaged and formed a gas-tight seal with both substrates. 60.The assembly of claim 59 wherein the interior surface of the insertbears more than two of such teeth, the teeth being separate andlongitudinally spaced apart from each other.
 61. The assembly of claim60 wherein the teeth are arranged pairwise such that individual ones ofpairs of the teeth protrude inwardly from the body of the insert atpoints equidistant from the mid-section.
 62. The invention of claim 28or 59 wherein the insert is formed of a gall-prone metal.
 63. Anassembly comprising:(a) a pair of substrates; (b) a tubular, metalliccompression sleeve that has been heat-recovered by being heated aboveits transition temperature; and (c) a tubular, metallic insert, theexterior surface of the insert bearing at least one radial toothcircumferentially formed about the longitudinal axis of the insert, andthe interior surface of the insert being essentially devoid ofdiscontinuous design features such as teeth, the insert being snugly andconcentrically disposed within, adjacent to, and in contact with theinterior surface of the compression sleeve and in contact with theexterior surface of both substrates, wherein when the compression sleevewas hear-recovered by being heated above its transition temperature, theinsert was altered in at least one of its dimensions and was driveninwardly by the heat-recovered sleeve for securely engaging and forminga gas-tight seal with both substrates.
 64. The invention of claim 63wherein the exterior surface of the insert bears a plurality of suchteeth, the teeth being separate and longitudinally spaced-apart fromeach other.
 65. The invention of claim 1, 28, 44, 59 or 63 wherein theinsert protrudes from opposite ends of the sleeve and is not greater inlength than about the quantity L +2 Di, where L is the length of thesleeve and Di is its internal diameters.
 66. The invention of claim 65wherein the insert is not greater in length than L+Di.
 67. An assemblycomprising:(a) a pair of hollow substrates; (b) a metallic driver thathas been heat-recovered by being heated above its transitiontemperature; and (c) a tubular, metallic sleeve, the interior surface ofthe tubular sleeve bearing at least one radial tooth circumferentiallyformed about the longitudinal axis of the sleeve, the exterior surfaceof the sleeve being essentially devoid of discontinuous design featuressuch as teeth, the sleeve being snugly and concentrically disposedadjacent to, in contact with, and surrounding the exterior surface ofthe driver and in contact with the interior surface of both substrates,wherein when the driver was heat-recovered by being heated above itstransition temperature, the sleeve was altered in at least one of itsdimensions and was driven outwardly by the heat-recovered driver forsecurely engaging and forming a gas-tight seal with both substrates. 68.The invention of claim 14 or 67 wherein the interior surface of thesleeve bears a plurality of such teeth, the teeth being separate andlongitudinally spaced-apart from each other.
 69. The assembly of claim67 wherein the exterior surface of the sleeve has a profilometerroughness not greater than about 125 micro-inches.